The present invention relates to radio frequency identification (“RFID” herein) tags, and more particularly, to an RFID tag provided with means to detect and externally report information regarding an environmental condition.
Many different devices are known for marking, labeling, tagging or otherwise associating information with a host product regarding matters such as the identity, source, nature, price and/or other characteristic of the product. Such information is useful to inform consumers, end users, distributors, manufacturers and others who may handle, inspect or merely encounter commercial and other products distributed in a modern society.
Such known devices include printed text or graphic labels and tags of paper, card, plastic or metal which may be attached to a host product by various means such as adhesive, stitching, ties, rivets, or other fastening means, as well as electronically readable information such as magnetic or optical codes such as bar codes and the like. Another category of such information device the use of which is growing rapidly at the time of making the present invention comprises radio frequency identification devices, commonly referenced by their initials as “RFIDs”.
RFIDs are of particular interest for the ease with which they can be read, their low cost, the quantity of information that can be communicated, and the fact that this information is usually available in a digital form convenient for downstream data processing. In late 2004 they are being widely adopted in the United States with major organizations such as Wal-Mart and the US Department of Defense expected to require use of RFIDs by their vendors in the very near future. With such markets in view, the present invention contemplates and provides an innovative RFID device with novel useful capabilities.
In addition to the above-described identity and other information, it can often be useful to associate with a product historical information about an environmental condition, e.g. temperature fluctuations, to which the product has been exposed as such information may be relevant to the quality of the product during transport and storage and as well as to the product's quality when it reaches the consumer or other end user. Desirably, such information should be easily communicated and received externally of the host product. Various means are known for monitoring environmental conditions that are suitable for incorporation in information labels or tags associated with host products and which can communicate the environmental information externally of the host product. Such means include chemical sensors that report information visually and biochemical sensors that communicate electronically.
Sjoholm, et al. in U.S. Pat. No. 6,642,016 assigned to Bioett AB, describe one such information device, intended for incorporation with a product label to indicate the status of an associated product, which reportedly can sense and report environmental data as well as product identifying data. Sjoholm, et al. disclose a biosensor useful to indicate the status of a product which employs a sensor unit that employs an enzyme to contact a substrate in a manner changing the substrate's conductivity as a function of time and temperature. The sensor unit is included as a component in an electric circuit. According to Sjoholm, the electric circuit can be remotely activated by applying an electric field and/or a magnetic field over the electric circuit to generate a measurable resistance-indicating signal related to the substrate conductivity. The biosensor can be incorporated in a label to indicate the status of a host product. Biosensor signals together with product ID can be stored in a memory unit (column 8, lines 48–51) at a control station.
Sjoholm et al.'s proposed device is complex requiring a number of electrical components, and lacks provision on the device for product ID information. Furthermore, Sjoholm et al.'s lacks convenient indication of the probable condition of a host product and of how that condition relates to a freshness threshold of the product.
Thus, known environment-condition reading devices intended for tags or labels fail to provide the benefits of RFIDs, may be unduly costly, or complex and may have other drawbacks.
As is known in the art, for example from Paratore et al. U.S. Pat. No. 6,294,997, RFID devices or tags are small, low-cost wireless transponder devices equipped with nonvolatile memory for information storage, typically information about an item or host product to which the RFID tag is attached. For example, inventory items can carry RFID tags providing information such as serial numbers, price, weight, and size. RFID tags are capable of responding to wireless interrogation by wireless transmission of stored information for receipt by the interrogator. The term “RFID tag” is used herein to include self-supporting, self-contained tags, cards or labels that are attachable to a host product or product, continuous web tags separable into individual tags for attachment to a host product, RFIDs supported on a substrate or otherwise constructed for incorporation on or into a host product and any other RFID device suitable for association with a host product to transmit information regarding the host product externally of the product.
Use of RFID tags can permit efficient retrieval of information regarding an item at various points in the manufacturing and distribution chain, and can also permit tracking of the individual item. Some RFID tags permit relatively large amounts of data to be associated with the product. An RFID tag typically includes a memory, an RF transmitter, an RF receiver, an antenna, and logic for controlling the various components of the memory device. The antenna may be formed on a flexible substrate, while analog RF circuits and digital logic and memory circuits are embodied in an integrated circuit (“IC”) carried by the substrate and coupled to the antenna. RFID tags may also include a number of discrete electronic components, such as capacitors, transistors, and diodes.
RFID tags can be either passive or active devices. Active devices are self powered, typically by a battery. Passive devices lack their own power source and derive energy from the RF signal used to interrogate the RFID tag. Passive RFID tags usually include an analog circuit, which detects and decodes the interrogating RF signal and which provides power from the RF field to a digital circuit in the tag. The digital circuit generally executes all of the functions performed by the RFID tag, such as retrieving stored data from memory and modulating the RF signal to transmit the retrieved data. In addition to retrieving and transmitting data previously stored in the memory, the RFID tag can permit new or additional information to be stored into the RFID tag's memory, or can permit the RF tag to manipulate data or perform some additional functions.
The ubiquity of RFID tags and their convenience as low cost remote information reporters that can be economically employed to useful effect to provide information about a wide range of commercial and other products, has led to numerous proposals to exploit their low-cost communications capabilities to enable remote reporting of a variety of data regarding a host product. These proposals include RFID devices and systems for collecting and communicating environmental condition information.
For example, Brollier U.S. Pat. No. 6,667,092 discloses an RFID processor embedded in a corrugated structure between a linerboard and a corrugated medium. One or more sensors for ambient environmental conditions such as time, temperature, pressure, and humidity may be electrically coupled to the RF processor. The sensors may be utilized to read and transmit a signal corresponding to the environmental or other conditions when signaled by an RF reader.
Paratore et al. (supra) also discloses the use of sensors to monitor various conditions ambient to the host product. Paratore et al.'s RFID tag comprises a number of auxiliary electronic modules providing data regarding changes in various physical parameters which data can be supplied to the RFID tag memory and be reported externally in response to interrogation of the RFID tag. The auxiliary modules include a timing module 20 which employs a capacitor 21 (C3), a resistor 22 (R3), an A/D converter 24, a control circuit 26, and an N-bit register 28 to generate timing ticks. Environment module 70 tracks resistance values and their changes with temperature or employs a microsensor to evaluate an environmental condition that exceeds a certain threshold. Another embodiment of environment module 70 employs evaporation of a polymer to create a conductive circuit whose conductivity can be measured (by unspecified means) to determine temperature elevation. With 11 the assistance of timing module 20, reportedly, the duration that an environmental condition is elevated, as determined by environment module 70, can be determined. The information generated by environmental module 70, is converted to an appropriate number of timing ticks by timing module 20 and stored as digital data in memory 60 to be reported externally of the tag in response to interrogation. Paratore et al.'s device is proposed for use for monitoring the temperature or other conditions to which a perishable or degradable good, such as a foodstuff, may be exposed over time.
While it can be useful to detect and report an environmental parameter from an RFID tag, devices such as Paratore et al.'s and Brollier 's are complex, expensive and potentially cumbersome, and accordingly are unsuitable for certain applications. Pursuant to the invention, it has been understood that it would be desirable to provide an RFID tag which is capable of simply and economically monitoring an environmental condition.
The foregoing description of background art may include insights, discoveries, understandings or disclosures, or associations together of disclosures, that were not known to the relevant art prior to the present invention but which were provided by the invention. Some such contributions of the invention may have been specifically pointed out herein, whereas other such contributions of the invention will be apparent from their context. Merely because a document may have been cited here, no admission is made that the field of the document, which may be quite different from that of the invention, is analogous to the field or fields of the present invention.